/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <constants.h>
#include <ruby.h>
#include <thrift/lib/rb/ext/macros.h>

ID buf_ivar_id;
ID index_ivar_id;

ID slice_method_id;

int GARBAGE_BUFFER_SIZE;

#define GET_BUF(self) rb_ivar_get(self, buf_ivar_id)

VALUE rb_thrift_memory_buffer_write(VALUE self, VALUE str) {
  VALUE buf = GET_BUF(self);
  rb_str_buf_cat(buf, RSTRING_PTR(str), RSTRING_LEN(str));
  return Qnil;
}

VALUE rb_thrift_memory_buffer_read(VALUE self, VALUE length_value) {
  int length = FIX2INT(length_value);

  VALUE index_value = rb_ivar_get(self, index_ivar_id);
  int index = FIX2INT(index_value);

  VALUE buf = GET_BUF(self);
  VALUE data = rb_funcall(buf, slice_method_id, 2, index_value, length_value);

  index += length;
  if (index > RSTRING_LEN(buf)) {
    index = RSTRING_LEN(buf);
  }
  if (index >= GARBAGE_BUFFER_SIZE) {
    rb_ivar_set(
        self,
        buf_ivar_id,
        rb_funcall(
            buf,
            slice_method_id,
            2,
            INT2FIX(index),
            INT2FIX(RSTRING_LEN(buf) - 1)));
    index = 0;
  }

  if (RSTRING_LEN(data) < length) {
    rb_raise(rb_eEOFError, "Not enough bytes remain in memory buffer");
  }

  rb_ivar_set(self, index_ivar_id, INT2FIX(index));
  return data;
}

void Init_memory_buffer() {
  VALUE thrift_memory_buffer_class =
      rb_const_get(thrift_module, rb_intern("MemoryBufferTransport"));
  rb_define_method(
      thrift_memory_buffer_class, "write", rb_thrift_memory_buffer_write, 1);
  rb_define_method(
      thrift_memory_buffer_class, "read", rb_thrift_memory_buffer_read, 1);

  buf_ivar_id = rb_intern("@buf");
  index_ivar_id = rb_intern("@index");

  slice_method_id = rb_intern("slice");

  GARBAGE_BUFFER_SIZE = FIX2INT(rb_const_get(
      thrift_memory_buffer_class, rb_intern("GARBAGE_BUFFER_SIZE")));
}
